SFTP performance question

I am testing sFTP library from SecureBlackbox and CallbackFS. So I don't know if this post should be in this forum section or rather in CallBackFS's one.

I wrote a piece of software which works as your SFTP Net Drive. I am using .NET C# CallbackFS and SecureBlackbox API and Visual Studio 2010 on Windows 7 64 bit machine and .NET framework 4.0.

The question is the performance. I tested my software with local virtual machine with Fedora 16 running standard sshd as a SFTP server. With my software I can achieve about 2.5MB/s both for read and write tests. When I tested the SimpleSFTPClient and SophisticatedSFTPClient from samples the performance was similar to my software. But the SFTP Net Drive can achieve 10-13MB/s using the same sFTP server! I belive that SFTP Net Drive was written using both CallbackFS library and sFTP library from SecureBlackbox so, in theory, i can achieve similar performance for my software.

I spend some time trying to tune some CallbackFS parameters andSecureBlacbox sFTP parameters for my software but it didn't improve the performance.

Can you give me some tips or specific sFTP configuration parameters from the SFTP Net Drive which makes sFTP transfer so fast.

I attach my configuration for CallbackFS and SecureBlackbox (not listed options are set to default values). Maybe here is the problem:

The main difference between SFTP Net Drive and your application is that SFTP Net Drive is based on SecureBlackbox VCL edition and is compiled into a native code that is faster than pure managed .NET code. Another reason could be that you use a trial license key. A trial version of Secureblackbox includes time delays, which occurs during execution of certain methods. You can request a trial key without time delays here: http://www.eldos.com/sbb/keyreq/

Thank you for fast responses.
A am using time-limited SecureBlackbox key without delays fr om Eugene. I also read these articles and tried all these tips without significant performance improvement.

Maybe the bottleneck is managed .NET code as Vsevolod wrote.

Can you write the approximate maximum performance you can achieve with .NET sFTP SecureBlackox library in your tests? Of course if it is not a secret ;) Maybe the 2,5MB/s is the lim it for managed code and i have to rewrite my project with SecureBalckbox VCL edition to improve the transfer speed.

Speed depends on plenty of factors including used encryption algorithms. You can experiment with various algorithms (especially you need to disable DES and 3DES). Also .NET JIT compiler has a problem with AES on some computers - the code works much slower than on most other systems. Normally AES code is only 5-10% slower, than in VCL, but on those problematic computers speed can decrease in about 50%.